The present invention is related to the field of actuators for position-controlled elements such as flight surfaces of an airborne vehicle.
Electro-mechanical actuators are generally known which provide mechanical power to establish and maintain the position of a position-controlled element (PCE), which may include fins, flaps and other flight surfaces of missiles or other airborne vehicles. The mechanical power is generated by a motor and coupled to the PCE via a mechanical drive linkage. Operation of such an actuator is typically controlled by a control circuit or unit (generally “controller”) which is responsible for accurate positioning of the PCE responsive to an input positioning command signal from some other element of the system. In an airborne vehicle, for example, the positioning command signal may be from a navigation controller which is responsible for moving the airborne vehicle along a desired flight path, and it may represent an angle value which is the desired angular position of the PCE.
One general class of controller for electro-mechanical actuators is the so-called proportional-integral-derivative or PID type of controller. A PID controller may receive a motor position feedback signal from a Hall-effect sensor or other position sensor, and it may use the position feedback signal in a conventional manner to position the PCE as commanded by a position command signal, based on an assumed known relationship between the motor position and the position of the PCE.
U.S. Pat. No. 7,276,877 of Qiu et al. shows a controller for a motor drive system of a type commonly used in aerospace and industrial applications. A state observer control system for the motor uses an extended Kalman filter to predict initial rotor position and afterwards accurately predict rotor position and/or speed under variable types of loading conditions. A control system model is generated that allows variable setting of an initial rotor position to generate estimated rotor position and speed as outputs. The control system model includes an EKF (extended Kalman filter) estimator, speed controller, a current controller, and a variable load component. During operation, EKF estimator estimates rotor speed and position based on reference voltages and currents generated by speed and current controllers and input from frame transformers. Additionally, the reference currents and voltages are frame-transformed to be used as feedback signals in the system and as drive signals to control power to be applied to a motor load.
U.S. Pat. No. 6,564,110 of Makino et al. shows a motor-drive controller including a discrete Kalman filter and a disturbance estimating unit added to a feedback loop for feeding back a detected value of position from a position detector. The Kalman filter estimates position and velocity of an object to be controlled, thereafter outputting an estimated value of position and an estimated value of velocity. The disturbance estimating unit estimates the current value of the disturbance that is applied to an object from a command value of current and the estimated value of velocity. The estimated value of position is fed back to a position controller, and the estimated value of velocity is fed back to a velocity controller. Further, a difference between a target value of current outputted from the velocity controller and the estimated value of disturbance is output as the command value of current.